Hydrodynamic machine



g- 4 W. FERRIS ET AL 2,406,138

' v HYQDRQDYNAMIC- MACHINE Filed Jan. 14, i942 6 Sheets- Sheet 2 'INVEAIITORS; WALTER FE'RRIS v .ADULF R. BRAD AT TDRNEY.

Aug. 20, l9 46.- V w. FEIRRIIS ET AL v HXDRODYNAMIC MACHINE- Filed Jan. 14, 1942 6 Sheets-Sheet 3 Juiszvr'oas WALTER 'F'ERRIS .ADDLF H. GRAD AT TDRNEYZ Aug. 20,1946. w. FERRIS ETAL 2,406,138

' HYDRODYNAMIC MACHINE Filed Jan. 14, 1942 6 Sheets-Sheet 6 mvtmoxsg WALTER Fenms ADDILF F1. GRAD ATTORNEY.

Patented Aug. 20, 194-6 UNITED STATES 2,406,138 HYDRODYNAMIC MACHINE Walter Ferris, Milwaukee and' Adolf R. Grad,

Wauwatosa, Wis., assignors: The-oilg'ear Company, Milwaukee, Wis., a corporation of Wisconsin Application January 14, 1942, Serial No. 426,702

22 Claims.

This invention relates to hydrodynamic machines of the type which has cylinders arranged in a rotary cylinder barrel, a stationary valve having inlet and outlet ports with which each cylinder-communicatesalternately as the cylinder rotates, a piston fitted in each cylinder, and a reaction member arranged around the cylinder barrel in contact with the outer ends of the pistons and having its axis oflset from the axis of the cylinder barrel when the machine is performing useful work. "Such a machine will function as a pump when driven from a source of power orit will function as a motor when supplied with motive liquid.- I

One object of the invention is to provide a machine which i's very small in size relative to its'power capacity.

Another objecti's togreatly increase the number of pistons and cylinders without materially increasing the size of the cylinder barrel.

' Another object is to provide a hydrodynamic machine of the'rolling piston type with a cylintier-barrel in which the pistons and cylinders are so arranged as to neutralizethe axial components of the forces transmitted-through the pistons.

Another object is to provide a hydrodynamic machine with a flat va-lvdmember having the passages so arranged therein that the bearing area of the valve member may" be reduced to a minimum.

Another object is toprovide means for preventing the high pressure liquid from lifting the flat valve member of a hydrodynamic-machine fromits seat particularly when the cylinder bar'- rel is rotating at a low speed.

' Another object is to provide a hydrodynamic" machine with a control which in response to the application theretoof an-external force will vary the displacement of the machine and which will automatically reduce the displacement of the machine to zero upon the external force being permit or to cause the reaction member to move. in one direction or the. other and the path of the cam is positively determined by a. roller bearing." A.v hydrodynamic machine constructed according. to. the invention has the advantage. 'of' being.

positive and precise in operation and susceptible of extremely close adjustment and control,

{Qt'her objects and advantages-will appear from i the description hereinafter given of a hydrodymachine in which the'invention is em bodied. l

Since the same hydrodynamic machine will function either as a pump or as a motor and since the function of a motor isthe reverse-of the function of a pump, the invention will be explained as applied to'a pump in order to simplify the description but it is to he understood that the" invention *isequally applicable to amotor and that the invention is in no way limited by designating' the machine as a pump. V

The invention is exemplified by the hydrody nanric machine shown partly in detail and in A part diagrammatically inthe accompanying 1-6' drawings in which the views are as follows:

, Fig; l is alongitudinal section througha'pum'pin which the invention is embodied, the view be ing taken on the irregular line |'-lof Fig; 2. Fig. "2- is a transverse section taken" on the ir- Fig. dis an elevation partly in section of the cylinder barrel of the-pump.

Fig.f4- isa section taken substantially on the irregular line 4-1 of'FFi-g.-3-. 25 Fig. 5- isa perspective view of the valve memberofthe-pump.

Figs. 6" and '7 are sectional plan views taken through the valve member and a part of'theend head of the pump'casing as indicated, respec- 36- tively by'lines 6-4 and- 1-4 of Fig. 5

Fig. 8 is a section taken onthe'line 81-8 of Fig. 1."

Fig. 9 is a sectional view showing a part of the r pump control mechanism, the view being taken substantially-on the line 9-9 of Fig. 2.

Fig. 1 0 isa sectional view showing another part, of the pump control mechanism, the view being taken substantially on theli-ne I0-l0 of Fig. 2. Fig. l1 is a view showing-a detail of a cam for 40" varying pump-displacement.

Fig. 12 is a diagrammatic view showing the hydraulic circuit of the pump and, illustrating the'methodof controlling pump displacement.

- Figs. l3aand 14 are face views, respectively, of

the valve seat and valve member of a hydrodynamic machine of larger capacity than the machine shown in Fig. l. V

Fig. 15 is a section taken on th line l5l5 of Fig: 1 p

Fig. 16 i'sa section taken on the line li -4 6 of Fig.14: f 1

The pumpchosen for illustration has its pumping mechanism: arranged within a casing I which is closed at its rear; end by a rear head 2" and 55 at its front end by a front head 3 having attached thereto a gland 4 through which adrive shaft extends for connection to a source of power.

I Shaft' 5 has its front part journaled in a bearing 6 carried by front head 3 and its rear part fixed to a cylinder barrel 1 which is rotatably supported by a bearing 8 carried by casing I. For convenience in manufacturing, the rear part of shaft 5 may. be enlarged and firmly pressed 1 into cylinder barrel I to form'in efiect a part thereof as shown but cylinder barrel 1 and the rear part of shaft 5 may be formed integral with I each other and the front part of shaft 5 either 1 formed integral therewith or connected thereto.

A piston 9 is fitted in each of a plurality of 3 cylinders In which are formed-in cylinder barrel l and communicate with a plurality of passages ID are inclined to the cylinder barrel ax'is and the outer end of each piston 9 is so shaped that it engages ring I 6 upon a single spot which is offset at such a, distance from the piston axis that the variation in the linear speed of the outerend of each piston relative to the speed ofring |6 causes thepiston torotate in its cylinder as it-reciprocates therein. V

In order to provide the maximum number of cylinders in a cylinder barrel of a-given size, alternate cylinders are inclined in opposite directions in respect to the cylinder barrel axis. If all of the cylinders in a cylinder barrel were in the same plane, the inner ends could be arranged close together with only a wall of the necessary 7 thickness between adjacent cylinders but the II formed in shaft 5 and extending through its 7 rear'end which forms a seat I2 for aflat faced valve I3 having two arcuate grooves or'ports I4 3 and I5 formed therein. Passages II constitute cylinder ports each of which registers with valve ports I4 and I5 alternately as cylinder barrel 1 1 rotates and, in order that one cylinder port may not open to one valve port at thesame instant that another cylinder port opensto the. other valve port, an odd number of passages are providedL As shown, shaft 5 has seven-passages II formed, therein and each passage communicates g with two adjacent cylinders I0 whose axes slope in opposite directions.

The outer ends of pistons 9 engage the inner f faceof a thrust ring"; which, since the pump chosen for illustration is very small, has been shown as constituting. the inner race of a roller 1 bearing If! the outer race of whichis formed by the annular inner surface of a slide block I8,-

1 thereby savingthe spaee that the inner and outer 1 races of the roller bearing would ordinarily oc- ,cupy.v Ring I6 is restrainedfrom axial move- I ment by suitable flangescarried by cylinder barrel-1. Thrust ring It, rollerbearing I1 and slide I block I8 constitute a reaction memberfor effect ing reciprocation of pistons 8 when cylinder barrel I is rotated and the-axis .of thrust ring I 6 is offset fromthe'axis of cylinder barrel 1. t 7

Slide block l 8 may be supported upon slide plates according to the usual practice but it has beenjshown supported upon fourrollers I9 which are arranged at its four corners and permit it to be moved transversely of they cylinder barrel axis -to varypump displacement but restrain it from vertical movement, axial movement of slide 7 block IS being prevented bycasing I and front head 3. Slide block I8 constitutes one race for each roller I9 and thereby saves valuable space.

3 when cylinderbarrel I is rotated, the friction between the outer ends of pistons 9 and ring I6 jcauses ring I6 to rotate substantially in synchronism with cylinder barrel 1. When slide block I8 is shifted from its neutral position so that the axis ofring I6 is offset fromthe cylinder barrel axis, each piston 9 will move progress'ively outward an'd draw liquid into its cylinder I0 during one half'of each revolution of cylinder barrel 'I- and it will move progressively inward and expel liquid from its cylinder during the other'half of each revolutionof cylinder barrel 7. s I

I" The distancebetween the outer end of each piston and the cylinderbarrel axis thus constantly varies with a resultant variation in the linear speed of the outer end of each pistonrelative tothe substantially constant speed of ring outer ends of the cylinders would be spaced far enough apart to provide sufiicient space for another cylinder between each two adjacent cylinders. Therefore, by inclining alternate cylinders in opposite directions, approximatelyv twice as many cylinderscan be formed in the cylinder barrel.

Due to the distance between the outer end of each piston 9 and the axis of cylinder barrel 1 varying when cylinder barrel 1 is rotated and ring I 6 is eccentric thereto, the-outer end of each. piston 9 has a small movement axially of ring I6 and, when pumping forces are being transmitted from ring I6 to the pistons, this movement causes cylinder barrel 1 to be subjected to a horizontal force which tends to move it axi der pressure will be delivered 'tocylinders IIli through one port I4 or I5and liquidfat a low pressure will be discharged from cylinders. I0 through the other port I4 or I5.

Regardless of whether the machine functions as a pump or as a motor, the liquid in one of the valve ports is under a high pressure, theliquid in the other valve port is under a low, zeroor negative pressure, minute quantities of liquid will escape from the'high pressure port and spread over valve seat I2 and the face of valve I3 to form a lubricating film therebetween, the pressure prevailingin the high pressure port will extend into the lubricating film, and the pressure prevailing in one or both of the ports and in the film will tend to move the valve away from its seat.

Due to the pressure being very high in one valve port and very low or absent in the other valve port, the film pressure varies from a high pressure'at the edge of the high pressure portto a low or zero pressure at the edge of the other portand to zero at the edge of thevalve seat.

Consequently, the center of pressure is not on the 'c'enter'of the valve but, if thepressure in the low pressure port is zero or'negative, the center ofpressure is near .the center of a high pressure area whichextends around the high pressure IB.. 'Inorder to avoid sliding friction'betweeni ri e! nd the germ f. P ns 9 y i d f port or, ifthere, is pressure in the low pressure.

port, there will be one center of pressure near the center f a high pressure area which extends around the "high pressure put and anothereen! ter of pressure near the center of a low pressure area whichextends around the low pressure port.

However, the force exerted by the liquid in it being understood that the center of high pres sure is on one side of the cylinder'barrel ax-is when one port is the high pressure port and on the other side of the cylinder barrel axis when the other port is the high pressure port. I

In order to limit the area of the film into which pressure may extend, a recess 20 is formed in-the'frace of valve 13 at the center thereof, a limit groove 2| is for-medi-n the 'face of valve-l3 between the periphery thereof and the outer edges of ports [4 and -l5,-and drain ducts- 20 and 2|" extend, respectively, from recess 2ll-and grooves 2| rearwardthrough valve I3 so that liquid entering'recess 26 and groov 2| maydrain into casing I. The area of valveface outside of groove 2| simply acts as a bearing area as there is no pressure in the filth between it and seat '12.

In order that valve l3 may not be moved away fromits seat l2 by the pressure in the valve port and in the lubricating film, it is urged toward its seat by a constant force and by forces which vary in accordance with variations in the pressure prevailing in the valve ports.

As "shown'in Figs. land 5, port l4 communicates with a passage '23 which extends through valve l3 into alinement with a bore 24 formed in rear head 2 and communicating with a pas-- sage 25 which extends-outward'through rear head 2 for connection to an external circu-it. A'substantially fluid tight joint between passage 23 and bore 24 is provided by a thimble 26 having its front end forming a flat slidable joint with the rear face of valve l3 and its rear end forming a substantially spherical joint with a tubular hold-up piston 21 which is fitted in bore 24 and urged against thimble 26 by a spring 28 arranged in the rearend of bore 24. Passages ll, port I4, passage 23-; thimble. '26, the bore through piston 21, bore 24 and passage 25*form' a channel for the flow of liquid between cylinders l and one side of an external circuit.

As shown in Figs. and 7', port l'5 communicates with two passages 29 each of which extends through valve I3 into alinement with a bore 3li-formed in rear head 2 and communicatingwith a passage 31' which extends outward through rear head 2 for connection to an external circuit. A substantially fluid tight joint between each passage 29 and a bore 30 is provided by a thimble 32 having its front end forming a flat slidable joint with the rear face of valve l3 and its rear end-forming a substantially spherical joint 'with a tubular hold-up piston 33 which is fitted in bore 30 and urged against thimble 32 by a spring 34 arranged in the rear end of bore 30. Passages ll, port l'5, passages 29', thimbles 32, the bore through pistons 33, bores 30 and passage 31 form a channel for the flow of liquid between cylinders I0 and the other side of an external circuit.

Thimble 26 is held against valve I 3 and piston 21 is held against thimble 26 by spring 28, each thimble 32 is held against valve l3 and each piston'33 is held against a thimble 32 by a spring 34-, and valve [3 is held against its seat I: by

spring 28 and-both of springs 34 so that valve I3 is constantly urged against-its-seat 12 a constant 61 force which is .proportional'to the c'ombinedre sis'tances of springs-28 and :34. v I;

- The pressure in bore 24- u the same as the pressure in port l4 and this pressure acts upon 1 the end of piston 21 and causes it to urge valve" l3 against its seat "with a force which is proportional to andvaries in accordance with varia-v tions in the pressure in port 1 4'. "The pressure ineach 10f bores 30 is the same as the pressure.

in port'ili and this pressure acts upon the-end of piston 33 and causes it to urge valve r 13 against its seat with a force which is proper-- tional to and varies in accordance with variations'in'thepressureinport l5. Each hold-up piston and the bore in which it is fitted constitutes a hold-up motor andthe" several hold-up motors are so proportionedt-hat, regardless of which of ports l4 and I5 is the high pressureport, the hold-up force applied to.

valve 13 exceeds the force tending to-move it away from seat l2 by an amount which is great enough to hold valve I3 against seat 12 but "is" not great-enough to cause an-unnecessaryfr ictional drag upon seat I 2 during rotation thereof relative to valve l3.

The hold-up motors are so arranged that tl ie force exerted by a hold-up motor or the resultant of the forces exerted by a group of hold-up motors on one side of th cylinder barrel axis is applied to thevalve at a point which is approximately opposite the pressurecenter 0f the-- pressure area surrounding the valve ports cn-the same side of the cylinder barrel'axis.

If a single hold-up motor or the same riurnbe of hold-up motors were arranged upon opposite sides of the cylinder barrel axis of a small m-a-fi chine, corresponding 'motors would necessarily be of the same diameter and it would be impossible to arrange them close enough together to apply r th hold-up forces to the proper points on the valve without increasing thediameterof the valve: and the valve seat tosuch an extent that the" overall size of the machine would be materially increased and the frictional drag on the valve seat increased so much that the efficiency'ofthe machine would be seriously impaired.

The present invention, however, provides a different number of hold-up motors of different diameters upon opposite sides of the cylinder barrel axis so that they maybe arranged close together and the efiiciency of the machine maintained' while reducing overall dimensions to a minimum. While the machine has been shown provided with one h'old-upmotor on one side of the cylinder barrel axis and two smaller holdup motors on the other side thereof, it is obvious that agreater number of hold-up motors could be provided, particularly in a machine of greater capacity, providing that a greater number were arranged upon one side of the axis than upon the other side thereof.

7 As best shown in Fig. 5, ports I! and [5' are separated from each other at the ends thereof'by I valve areas which are generally known as bridges and provide seals between the two ports; thatis, the length of each bridge is at least as great as the diameter of the cylinder ports which in this case are the ends of passages l I.

When the machine is performing work, high I pressure prevails in the cylinder ports communicating with the high pressure valve ports and in the cylinder port Which has just passed onto a bridge from the high pressure Valve port but has I not opened to the low pressure valve portjglow pressure prevails in the cylinder ports cornmuni'-- lyvary as the cylinder barrel rotates. plain the machine shown there will be four high pressure cylinder ports and three low pressure cylinder ports at oneinstant and three high pressure cylinder ports and four lowpressure cylinr When the machine isoperatingat high the sizeof the pressure area and th location of the center of pressure change so rapidly that properly located hold-up motors ;will hold the cylinder port which has just passedonto abridge from the low pressure. valve port but ha not opened to the high pressure valve port; and the number of high pressure cylinder ports and the number of'low pressure cylinder ports continuous- For examder ports at the next instant. This variation in th number communication with the high pressurevalve port.

The pressure area is suddenly reduced by a cylinder port containing liquid under high pressure moving from one bridge into communication with the low pressure valve port and it is gradually reduced as the cylinder port moves off the other bridge into full registry with the high pressure valve port. Extending th pressure area on one or both bridges causes the center of. pressure to move from the center of pressureof the minimum pressure area radially inward and also ;parallel to the axis of the bridges.

valve to its seat but if the machine is operating atlow speed as when a motor is starting it load, thechange in the pressure'area' and in the center of pressure causes the valve to be tilted or to be lifted from its seat so that liquid can escape from between the valve and its seat to such an extent 1 thatunder certain circumstances the motor cannot start its load.

r i In order to prevent the valve from bein tilted or lifted from its seat, the hold-up motors are so 1 arranged that the force exerted by a single motor or the resultant of the forces exerted by a plurality'ofmotors is applied to the valve at a point 1 approximately opposite the center of pressure of the minimum pressure area and balancing mo-.

tors are provided to compensate for increases in the pressure areas and shifts of the centerbf pressure toward one bridge or the .other, the bal-j ancing motors being arranged behind the bridges and supplied with liquid through ducts which exj tend through the face of the valve. 7

If the machine is small and of the single phase, type as shown in Figs. 1 to 12, a single balancing motor is arranged behind each of the bridges. f As shown, a cylinder 40 (Fig. 6) is formed in valve [3 behind each of the bridges, apiston 4| is fitted in each cylinder 40 and bears against the front end of rear head 2, and a duct 42 extends from cylinder 40 through the face of the bridge. j outer ends of ducts 42 are usually located directly 1 in the path of the cylinder ports but they may be ofi'set therefrom.

The

As each cylinder port crosses a bridge, a pressure impulse is transmitted therefrom to th bal ancing motor behind that bridge through duct 42 either directly from the cylinder port or through i the lubricating film on the bridge. The pressure a j impulse energizes the balancing motor and causes of high pressure cylinderports causes the pressure area surround-i ing the high pressure valve port to vary'betweenj a minimum and a maximum and the center ofi pressure'of that area to move radially. The pres- 1 speed,

it .to;exerit upon valve seat 13 a hold-up force in additiongto thehold-up forces exerted thereon by I can escape through duct 42 from the balancing motor to substantially deenergize it. 7 Since extension of the pressure area and the shift of the center of'pressure is due to th pressure in the cylinder portsrac ting upon the bridges, the'ba1- ancingmotors are energized and deenergized in synchronism, with the changes in the center of pressure sothat valve I3 is held firmly to its seat without excessive hold-up force being exerted thereon. I

Thevolumetric capacity of a machine of the type shown is ordinarily increased by adding additional rows of pistons 9 and cylinders I 0 in whichcase the machine is ordinarily of the split phase type, that is, the cylinder ports are arranged in at least two concentri circular rows and the leading edges of the ports in one row are 'Figal.

offset from the leading edges of the ports in the other row so that the cylinder ports open successively to the valve ports.

For example, such a machine may be provided with avalve seat l2? which has a plurality of circular cylinder ports ll and a plurality of elongated cylinder ports I I formed therein in concentric circular rows as shown in Fig. 13, it

being understood that valve seat l2 is formed upon the end of the rotor of themachine in the same manner that valve seat I2 is formed upon I the end of the rotor of the machine shown in as small as possible the valve member I3 with 'which valve seat [2 coacts to control the flow of; liquid to and from the pumping cylinders;

Since valve l3 is functionally the same as the valve l3 previously described,.like parts have been indicated by like reference numerals with the exponent a added to the reference numer als applied to valve [3.

Since the cylinder ports are arranged in two.

concentric rows, the valve ports I l and l5 in valve I3 are made wide enough to register with both, rows of cylinder ports and the bridges bea tween the valve ports are wider at theirouter ends than at their inner ends and are so shaped as to completely cover each cylinder port as it centers uponabridge.

Since valve i is of substantial size, the same,

number of hold-up motors may be arranged upon opposite sides of its axis. Asshown, valve l3 has two passages 23 extending therethrough from port M and two passages 29 extending therethrough from port I5 Each passage 23 communicates with one side of a hydraulic circuit a through a hold-up motor of which only the tubular piston 21 and. the thimble 6 have beenv shown, and each passage 29 communicates with the other side of the circuit through a hold-up motor'of which only the tubular piston 33 and the thimbl'e 32 have been shown. 7

In asmall machine. the pressure areas and but in' a large machine with a single balancing,

motor behind each bridge the errors in compensation result in larger unbalanced forces, and in irregularities of movement which become conspicuous atlow speeds. Therefore, 'a-large size machine ordinarily has a plurality of balancing motors arranged behind each bridge and adapted to be successively energized and deenergized.

Ports ll are elongated in order to keep As shown, valve I3 has six balancing'motors Eli -M arranged behindaeac-h' of: its.bridges.,. a duct fl -leads fromeach cylinder 40 throughthe face of valve l3a, one half of ducts 42 have. the outer ends thereof arranged in thezpath'of cylinder ports. He and the other h'aliof ducts 42 have the outer ends thereof arranged in. the path of cylinder ports Iii- Theouter: ends of du'cts42 'are-so spac'edth'at each. cylinder port registers: first. with one then withtwo and then with-th'reeducts 42 andthen passesout of registry with the ducts successively so" that the hold-up motors 4.09-4li1ar1. successively energized and then; successively deenergized. Consequently, the forces, exerted by. the balancing motors: upon valve 1.3%" are varied at a rate which is approximately the same as the rate. at which the high pressure area varies.

While only six balancing motors have been shown behind each bridge, a larger number are employed in. large machines. In fact, a medium size machine ordinarily has;ten;balancing motors behindeach bridge.

' In order that the several parts of the hold-up motorsand' the balancing motors may be; retained his position.duringass'embly of the machine, rear head 2- and' valv l3 areconnected together" to form a sub assembly. As shown. in Fig. 1, a rear head 2'? has: two. pins 473- fixed. therein upon. opposite sides ofv its axis, the outer part of. each pin 43 isproyided' with a. suitable cannelure and arranged in a. bore formed. invalve. i3, and valve. [3 has fixed therein two dowels 4.4 each of. which passes: through. the canne'lure. of a.- pin 43 and holds valve 131 and rear head; 2' together but permit's valve I3' to move slightly in anaxial direction relative to rear head 2..

When. slide block'lil is in its central or neutral position, thrust ring I6 is concentric with cylinder barrel 1' and rotation. of cylinder bar:-

rel 1 will not cause reciprocation. of pistons 9.-

When slide block L8 is shifted from its. neutral position, thrust. ring [6. will. be eccentric to cyliinder barrel 1. and rotation; of. cylinder barrel 1 will cause the. pumpto. deliver liquid in; a. direction and at a. rate determined by the direction and distance-slide block l8 isv ofiset from i-tsjneutral position. If cylinder barrel 1 is rotated in a clockwise direction, shifting slide block l8; to.- ward' the 'leit inrespect to- Fig; 2 fromits neutral position will cause pistons 9 to discharge through passages ll port I43. passage 23; thimblelfitubular piston 21, bore 24 and through passage 25- to one side of an external circuit and, shifting sliide block 18: toward the right-in respect to Fig. 2

to Fig. 2 by a cam 5. which engages a contact member 5.1. fixed to or formed? integral with slide block i8.

Contact member is, retained in engagement with. cam 59: by a compression, spring: 52 which engages slide. block I.8' upon its. opposite side and constantly urges it toward the right. Spring 52 has sufiicient strength to: hold contact 5! in engagement with cam 56 atall times and tomove slide block l 8 t its: neutral position from. its

. extreme; position at the left in which movement of; slide block, LB spring 52 .is assisted thrust of pistons 9" against ring l6.

Since the strength of a: compression spring; decreases :as it expands'and since the movement of the slide block toward the right from its neutral position is opposed by the thrust of pistons 9 against thrust ring [6,, spring 52, is assisted'in moving slide. block I8, toward the right from-its neutral position by a piston 53 fittedin a cylinder 54 which is carried by casing l and connected by a channel 55 to passage 31 as shown in Fig. 12.. The arrangement is such that, when cam-SIi-is the shifted; spring 52 will'move slideiblock. l8itoward ton 53110 assist. spring 52,-inmoving slide block 118' farther-toward the, right. a i

Asshown in Fig. '2, cam 5'05 has a head: 56 formed upon one end thereof and arranged within a hollow piston- 51 which is: fitted in a cylinder 5'8 -ca-rried by casing l, and a: head- 59 is'formed upon: the other end of: camv 50' and. arrangedrwithiin a hollow piston 60: which is larger than; piston 5-1 and fitted in'a cylinder 6| carried by. casing l in axial'alignment with cylinder 58..

Cam- 50 is ordinarily" so. shaped that: when contact 5| is in; engagement. with them-id-portion of cam 50, the movement of slide block .l:8:is

slight relative to the. movement of camill but I progressively increases as. contact 5| engages points on cam 50 which are; progressively farther from the mid-portion thereof;- 'As shown, cami'fl has: formed upon the face thereof'a cam track consisting of a short central'track section 6?; (Fig. 11)- which extends parallel to the path'of. the cam, a track section 6'3 which extends from; one end f section 62 toward piston 51 and-zis incline-d toward slide block F85, and a track. section 64' which extends. from the other endofi section 62' toward piston 60 and is inclined away from slide'bloclelflt. I

When cam 50' is in its neutral position as shown in Fig. 2, contact member 5-1 "will be in engagement with track'section 62 and slideblock 'l'fi wil'l be in its. neutral position so that pump displacement will be zero. When cam 50. is shifted upward in respect to Fig. 2; track section 63 will pass across contact 5 and move slide block t8 toward the left and thereby cause the pump to discharge liquidinone direction and to increase its'rate during continued movement of cam 50. When cam 50 is shifted downward in respect to Fig. 2;track section 64 will pass before the pump-can deliver liquid under pressure to an external circuit.

Ln order that the pump may deliver liquid to an external circuit. as soon as track section 63 or .64 engages contact 5|, the end of tracksectime 61 rises abruptly from one end oftrack sec tiOn: Gland the end of track section 64."drops j gagem'ent with roller into casing I.

abruptly away from the other end of track sec tion 62 as shown in Fig. 111 The length of track section 62 and the drop from one section toan- 'other has'been magnified in Fig. 11 forthe purpose of illustration but vin practice track section 62 is' very' short and in a small pump such as shownthe drop from one track section toanother is only a few thousandths of an inch as thatamount of movement of slide block I8 is all that is' necessary to cause the pump to supply liquid to compensate for leakage losses at a normal operating pressure.

' In orderthat slide'block 18 maybe adjusted exactly to its neutral position and in order to protect pistons and 68 from. the transverse thrust exerted upon cam 58 by slide block I8,

cam 58 issupported at a point opposite contact 5| and at'le'ast oneof the pistons 5'! or 68 is fitted loosely over the head on the e'nd of cam 58;

; As shown in Fig. 2, head -59 is slightly smaller than the bore in piston 68 and a roller 65 is inclined to' the plane of cam 58 and fitted in a bore which is formed in casing'l as shown in Fig.9. One end of roller '65 is approximately 1 spherical andengages the-back ofcam 58 at a point opposite contact 5| and the other end of roller '65 is fiatand in engagement with a ball 81 which is arranged in bore and held in en- 65 byia screw 68 threaded When contact 5| is in engagement with cam track section 62, screw 68 is'so adjusted that slide block I8 is held exactly in its neutral position sothat the pump is at zero stroke, thecleariance between head 59 and the interior of piston 68 compensating for any misalignment of parts and, for' any lateral movement of cam 58 neces sary to move slide block I8 exactly to its neutral position.

.: Whencam 58 is shifted in one direction or the i .other, roller'65 will rotate in cylinder 66 and pro- 1 wide an antifriction bearing for preventing any deflection. of cam 58 and for relieving pistons 51 f and 68 from the transverse thrust of slide block I8 against cam 58.

and closed at its rear pThe gear pump draws liquid from a reservoir 1 (Fig. 12) and discharges it into a channel 116 which is connected to channels and 3| 1 through check valves 11 and 18, respectively, so "that the power pump is supercharged by gear I pump liquid regardless of the direction of pump del1very. The liquid discharged by the gear pump in excess of requirements is'exhausted through a relief valve 19 which discharges into reservoir I5. The power pump i also provided with relief "valves 88 and 8| which are connected, respec- 1 tively, to channels 25 and 3| and permit'th es- 1 cape of liquid whenever the pressure created by the power-pump exceeds a'predetermined maximum. The delivery -of gearpump liquid to cylinder 1 6| is under the control of a'pilot valve 82 (Figs. 2, '10 and 12) fitted in a valve casing 83 which is carried by the pump casing and provided with threeannular grooves or ports 84, 8'5 and 86.

Port '84 communicates with a drain channel 81 which discharges into reservoir 15,-p rt 85 is connected'by a channel. 88'to cylinder 6|; and

port 86 .communicateswitha channel 89 which is connected to gear pump supplychannel 16-and to cylinder 58 so that piston 51 is gear pump pressure at all times.

When pilot .valve 82 is in its neutral positio it blocks" port 85 so that no'liquid can flow to or escape from cylinder 6| butacvery light movement thereof in one direction will open port 85 to port'84 so that liquid can escape from cylinder 6| and therebypermit the pressure in cylinder 58 to cause piston'5'l tomove cam 58 ;in-on direction and a very slight movement of pilot valve 82 in the opposite direction will open port 85 to port 86 so-that gear pump liquid can flow to cylinder 6| and cause piston 68 to move cam 58 in the opposite direction against-the force exerted thereonby piston '51 which is smaller thanpis toniiII. T' '1 The control for. pilot valve 82 includes followup mechanism which transmits motion from cam 58 to'valv'e 82 and tends to return it to its neuing one en'dthereof pivoted to the stem of valve 82 and the other end thereof supported by a pin '92 which is guided in the pump casing and bears upon a cam track 93 formed upon cam 59,a screw 94 being threaded through'the end of lever 9| into engagement with pin 92 for the purpose of adjusting lever 9| relative to cam track 93.

Lever 9| is operated by a shaft 95 journaled in casing I and having formed upon its inner end an eccentric 96 which engages lever 9| intermediate the ends thereof. Spring 98 urges lever 9| against eccentric '96 and causes adjusting screw 94 to bear upon pin '92 and pin '92 to bear upon cam track 93 soithat there is no lost motion between these parts at any time. V Shaft 95 is also J'ournaled in and restrained from axial movement by a spring retainer 91 which is fastened to casing I. A'torsion spring 98 is arranged around retainer 9'! and around a -'hub 99 which is fixed upon' the outer end of shaft 95 and provided. with means forflrotating it and shaft'95, hub 99 being shown provided with one part I88 of a ball and 'a socket joint by means of which it may be connected to a control device.

Spring '98 has its two ends arranged upon opposite sides of two pins 'I8I and I82 which are fixed, respectively, in retainer 9'! and hub 99 parallelwith each'other so that when hub 99 is rotated in'one direction or the other by an external force, pin I82 will move away from pin |8I and thereby cause the tension of spring 98 to be increased'and, when the external force is removed, spring 98 will return hub 99 andshaft95 to and yieldingly retain them in their neutral positions. In order to limit the angular distance through which shaft 95 may be rotated, a recess I83 is formed in hub 99 and a stop bolt I04 i fixed in retainer 91 with its head arranged within recess I83 so that rotation of shaft 95 in either direction is limited by the head of bolt I84 ngaging an end wall of recess I83.

' The above described control will operate in the following manner, it being assumed that cylinder barrel 1 is being rotated in a clockwise direction in'respect to Fig. 12 and that gear pump II-12 is maintaining pressure in channel I6 and it besubjected to 113 not inrespect to. any other figure. or to the machine .as actually employed in. practice.

When shaft 95: is. in its. neutral position as shown, cam 50 and slide block |8 are in their neutral positions and ,pump displacement i zero. When shaft=95 is rotated in a counterclockwise direction from its neutral position, eccentric 96 will depress lever 9| which will pivot upon pin 92 and move valve 82 downward so that gear pump liquid can flow through valve casing 83 and channel 88 to cylinder 6|. Since piston 60 is larger than piston 51, it will move cam 50 toward the right and cause Piston 51 to expel liquid from cylinder 58 into channel '89.

Movement of cam- .50 toward the right causes cam track 93 .to'moveacros the end of pin 92 so that, since pilot valve. 8-2 and the right end oflever 9| are urged upwardby spring 98, the left. end oflever 9|, moves. progressively down- ,ward as. cam 59 moves toward the right. and valve 82 isv kept depressed only during continued rotationof. shaft .95.. Consequently, valve .82 will be returned to its neutral position. as. soon as rotation of shaft, 95 ceases.

Movement of cam '58 toward the right also causes. cam track -62 to move. out of engagement with contact andcamtrack B4 to. move across contact 5| so that spring '52 canmove. slide. block l8 upward which will cause the. pump to discharge liquid into passagev 3|. As. soon as the pump creates pressure in passage 3|, the. pressure extends through channel 55'. to cylinder 54. and causes piston 53 to. assist spring 52 in moving slide block |8 upward to increase the displacement and delivery of the pump. When shaft 95 is rotated. in a. clockwise direction, eccentric 96 will revolve upward and permit spring 98 to raise pilot valve 82.and the right end of lever 9|, th left end of lever 9| continuing to press pin 92 against loam track 93 due to the action of the spring 99. Raisingpilot valve 82 will connect channel 88 todrain channel tl' and thereby enable the gearpump. liquid constantly supplied to cylinder 51 to move cam expel liquid from cylinder 6| through channel 88 and pilot valve casing 83 into drain channel 81. 'Movement of cam 50 towardthe left causes cam track 93 to move across the end of .pin 92 and raise pin 92' and the left end of lever 9| so I that pilot valve '82 is returned to its neutral position as soon as rotation of shaft 95 ceases.

If contact member 5| is in engagement with cam track 8'3, movement of cam 50 toward the left also causes cam track 64' to move across contact 51 and shift slide block I'8 downward to reducepump displacement. "If contact 5| is in engagement with cam track 62', movement of cam 50 toward the left causes cam track 82 to move out of engagement with contact 5| and cam track 63 to move across contact 5|". Cam track 63 in moving toward the left across contact 5| will shift slideblock I8 downward and cause the pump to discharge into: passage .25. Thereafter, continued rotation of shaft 95 will cause pump dis placement to continue to increas until it reaches maximum-and rotation of shaft 95in a counterclockwise direction will cause cam '58 "tomove toward theright and reduce pumpdisplacement as explained: above.

58 toward the left and cause piston 60 to cam 5.0 is at the left of its neutral position 01'. to permit aspring98 to shift pilot valve 82; upward if cam 50 is at the right of its neutral position.

Shifting pilot valve 82 causes cam 59 to move toward its neutral position and cam track 93 to adjust the left end of lever 9| as explained above. When cam 5|] reaches its neutral position,, cam trackliZ engages contact 5| and holds slide block |.':8 in its neutral position and pilot. valve 82- will have been returned to its neutral positionso that the liquid incylinder 6| is trapped therein and holds cam 58 in its neutral position. If liquid should leak'from cylinder 6| and permit cam 58 to start to move toward the left, cam track 93 will raise pin 92 and causelever 9| to swing about eccentric 96 as a fulcrum and depress pilot valve to: desired positions. In order that the speed of the motor may bevaried at a. rapid rate when the loadzis. at a distance. from a desired position and varied micrometrically when the load approaches a desired: position,.;cam tracks 6.3 and 64 are-.so shaped that. a given'angular movement of shaft results in. a. very small movement of slide block |i8 when it is near .its neutral position and results in a much greater movement of slide block |.8 when it. is farther from its neutral position. As shown, the slope of each cam track is non-uniform and isv reduced to a minimum near the-junction of the. track with .camtrack 62.

The hydrodynamic machine illustrated and d scribed herein may be modified in various wa rality of cylinders arranged therein with the outer endsof saidcylinders: arranged approggi: matelyin a circular row and; alternate cylinders in. said row inclined. in. opposite. directions in respect to the. axis of. said cylinder barrel to thereby reduce the space required for said cylinders, means 'for connecting each cylinder to opposite sides. of. a. circuit alternately as saidcylinder barclose together in a staggered row, the cylinders whose inner ends are in the left side 'of said row bein inclined outward toward the right end of said cylinder barrel and the cylinders whose inner pends arein the right side'- of said row being inclined outward towardthe left end of said cylinder barrel so that said cylinders occupy a minimum amount of space, a p'iston fitted in each cylinder, a cylindricai reaction member encircling said cylinder'barrel eccentric thereto to engage said pistons and effect reciprocation thereof during rotation of said cylinder barrel, and means for connecting each cylinder to opposite sides of a circuit alt-er-nately'as said cylinder barrel rotates-w Y 3. In a hydrodynamicmachine, the combination'of a rotor having passages extending inward from an end thereof, means for-connecting each of said passages to opposite'sides'of a circuit alternately as said'rotor rotates, a plurality of radial cylinders arranged in said cylinder barrel with the inner ends thereof arranged close together in a staggered row, alternate cylinders in said row being inclined in "opposite directions in respect to the radii of said rotor and'a portion of each cylinder outward from the inner end thereof being arranged between the adjacent cylinders so that all of said cylinders are arranged a minimum amount of space, a piston fitted in each cylinder, and a cylindrical reaction member arranged" around said rotoreccentric thereto to engage said pistons and effect reciprocation 'tlit'ereof during rotation of said rotor, said member engaging each piston upon a single spot which is onset far enough from the piston axis to causethe piston to rotate in its cylinder as it reciprocate's therein,

" 4. Ina hydrodynamic machine having its pis- "tons and cylinders arranged in a rotatable cylinder barrel, a valve seat arranged upon said cylinder barrel and provided with ports which communicatewithsaid cylinders, and' means for-re- :cipr'ocating said pistons, 'the'combina'tion of a 'valve engaging said seat and provided upon opposit'e" sides of its axis with valve' ports with which ea'ch cylinder port communicates alternately as said'cylinder barrel rotates, and a plu- "rality' of hold-up motors adapted to hold said valve against said seat and so arranged that a greater number of said motors are upon oneside of the valve axis than upon the other side thereof so that said motors may be arranged close together. I v

5. In a 'hydrodynamic machine having a casing and pumping means arranged within said, casing and including a valve seat having cylin- 'der ports arranged therein, the combination of a valve engaging said seat and provided upon opposite sidesof its axis withvalve ports with which each cylinder port registers alternately during op- "eration of said pumping means, an end head car-v ried by said casing and 'provided with connections for, connecting said valve ports to a hydraulic circuit, a plurality of hold-up cylinders so arranged in said end head that a greater number of said cylinders are upon one side of the valve axis than upon "the other side thereofand each cylinder communicates with one of said valve ports and.

with one of said connections, and a piston fitted in each hold-up cylinder to urge said valve against said seat and having an axial bore to provide a I passage for the flow of liquid between the valve 1 port and the connection with which its cylinder mommunicates;

6 In a hydrodynamic machine having a casing and pumping means arranged within said casing and including a valve seat having cylinder ports arranged therein, the combination of a valve .member engaging said seat' and provided upon opposite sides of its axis with valve ports with which each cylinder port registers alternately .during operation of said pumping means, an end and for providing communication between said, valve ports and said connections, connectors fixed to one of said members and associated with the other of said members'and means vfor retaining said connectors in association with said other member so that said members and saidchold-up motors may be connected together to formasub-f assembly before beingassembled with other parts of said machine. v 7. In a hydrodynamic machine haVing-a-casing and pumping means arranged within said casing and including a valve seat having cylinder ports arranged therein, the combination of a' valve member engaging said seat and provided upon'o'p;

member against said seatand for providing comimunication between said valve ports and said connections, a plurality of pins each havinglone end thereof fixed in one of said members and the v ment therebetween.

8. In a hydrodynamic machine having its pistons and cylinders arranged in a rotatable cylin der barrel and a valve seat arranged upon said cylinder barrel and provided with a plurality of ports which communicate with said cylinders, the

combination of a valve engaging said seat and provided with high and low pressure valve ports fwith which each cylinder port communicates alternately as said cylinder barrel rotates, a plurality of hold-up motors arranged behind said valve to urge it against said seat, atleast one balancingfmotor for assisting said hold-up motors in urging said valve against said seat, and means for intermittently energizing and deenergizing said balancing motor in accordance with variations in the number and angular positions of cylinder ports communicating with said high pressure port.

9. In a hydrodynamic machine having its pistons and cylinders arranged in a rotatable cylinder barrel and a valve seat arranged upon said cylinder barrel and-provided with a plurality of Y cylinder ports which communicate with said cylinders, the combination of a valve engaging said seat and provided with inlet and outlet ports and with bridges therebetween so arranged that each cylinder port registers with said inlet and outlet ports alternately as said cylinder barrel rotates and said bridges provide seals between said valve ports, a plurality of hold-up motors arranged behind said valve to urge it against said seat, and a balancing motor arranged behind at least one of said bridges to assist said hold-up motors in holding said valve against said seat, said valve having a duct leading from the face of said bridge to the balancing motor behind it so that said balancing motor is energized by pressure transmitted thereto through said duct from cylinder ports passing across said bridge.

10. In a hydrodynamic machine having its pistons and cylinders arranged in rotatable cylinder barrel and a valve seat'arranged upon said cylinder barrel and provided with a plurality of cylinderports which'communicate with said cylinders,

the combination of a valve engaging said seat and provided with inlet and outlet ports and with bridges therebetween so, arranged that each cylinder port registers with said inlet and outlet ports alternately as said cylinder barrel rotates and said bridges provide seals between said valve ports, a plurality of hold-up motors arranged behind said valve to urge it against said seat, said hold-up motors being energized by liquid transmitted thereto from said. valve ports. so that the forces exerted upon said valve by said hold u'p motors vary in accordance with variations" in the pressures at said valve ports, and a balancing motor arranged behind each of said bridges to assist said hold-up motors in holding said valve against said seat, said valve having a duct leading from thelface of each bridge to the balancing motor behind it so that said balancing motors are energiz'ed' by pressure transmitted thereto through said dust from cylinder ports passing across said bridges.

11. In a hydrodynamic machine having its pistons and cylinders arranged in a rotatable cylinder barrel and a valve seat arranged uponsaid cylinder barrel and provided with a plurality ofcylinder ports which communicate with said cylinders, the combination of a valve engaging said seat and provided with inlet andoutlet ports and with bridges therebe'tween so arranged that each cylinder port registers with said inlet and outlet ports alternately as said cylinder barre1 rotates and said bridges provide seals between said valve ports, a plurality of hold-up motors arranged behind said valve to urge it against said seat, and a plurality of balancingmotors arranged behind each of said bridges to assist said hold-up motors in: holding said valve against said seat, said valve having a duct leading from each hold-up motor through the face of the bridge and the outer ends of said ducts being so located that each cylinder port as it passes across a bridge communicates successively with a plurality of said ducts.

12. In areversible pump having a displacement varying member shiftable in oppos te directions from a neutral position to cause the pump to deliver liquid in either of two directions" and to vary pump delivery from Zero to maximum in either direction, the combination of means for constantly urging said displacement varying member in one direction, means for moving said member in the opposite direction against the action of said urging means, a servo-motor for assisting said urging means in moving said member in said one direction, and means for energizing said servo-motor only after said urging means has moved said member in said one direction beyond its neutral position.

13. In a reversible pump having a displacement varying member shiftable in opposite directions from a neutral position to cause the pump to deliver liquid to one side or the other of a hydraulic circuit and to vary pump displacement from zero to maximum in either direction of pump delivery, the combination of means for constantly urging said displacement varying member in one direction to cause said pump to discharge into the first side of said circuit, means for moving said member in the opposite direction against the action of said urging means, a servo-motor for assisting said urging means in moving said member in said one direction, and means for connecting said servo-motor to said first side of said circuit so that it will be energized only after said member has been moved in said one direction beyond its neutral position.

14.'In a pump having a displacement varying member shiftable in opposite directions to vary 18 pump displacement, the combination ofa cam for moving said member in one direction and for limiting its movement in the opposite direction, a contact on said member, means for urging said member in said opposite direction and for; holding said contact against the face of said cam, means for moving said cam in oppoSitediI-jections selectively to effect movement of said rr -z mber in; o pposite directions selectively, and a guide arranged opposite said contact andin engagement with the back of said cam to absorb the thrust imposed upon said cam by said member.

15'. In a pump having a displacement varying member shiftable in opposite directions to vary pump displacement,- the combination of a oamfpr moving said member in one directio n and for limiting' its movement in the opposite direction, a contact on said member, means for urgingsaid memberin said opposite direction and Iorholding said contact against the face of said cam, means for moving said cam in opposite directions selectively to effect movement of saidmem ber in opposite directions selectively, a roller arranged opposite said contact and inclined to the path of said cam, said roller'havin'g one end arcuate and in engagement with the back; of said cam, means for rotatably supporting said roller, and means for prevnting said roller from movinggaxiallyto thereby enable it to absorb the thrust imposed up'on'said cam by said member. v p a 16. In a pump having a displacement varying member shiftable in opposite directions t'ovary pump displacement, the combination of a cam for moving said member in one direction and forlimiting its movement in the opposite direction; a contact on said member; means for urging said member in said opposite direction and for bolding said contact against the face, of said cam, servo-motor means for moving said cam in opposite directions selectively to effect movement of said member in opposite directions selectively and including a stationary cylinder and a piston fitted in said cylinder and so connected to said cam that. said cam may be adjusted relative to the axis of said piston, and a guide arranged opposite said contact and in engagement with the back of said cam to relieve said piston from the' thrust imposed upon said cam by said member.

17. In a pump having a displacement varying member shiftable in opposite directions to vary pump displacement, the combination of a cam for moving said member'in one direction and for limiting its movement in the opposite direction, a contact on said member, means for urging said member in said opposite direction and for holding said contact against the face of said cam, servo-motor means for moving said cam in op posite directions selectively to effect movement of said member in opposite directions selectively, a roller arranged opposite said contact and inclined to the path of said cam, said roller having one end arcuate and in engagement with the back of said cam, means for rotatably supporting said roller, means for moving said roller to and retaining it in an adjusted position to enable it to absorb the thrust imposed upon said cam by said member, said servo-motor means including a sta tionary cylinder and a piston fitted in said cylinder and so connected to said cam that said roller adjusting means may adjust said cam relative to the axis of said piston, and means for preventing said roller from moving axially to thereby enable it to absorb the thrust imposed upon said cam by said member.

18. In a pump having a displacement varying 'member'shiftable in opposite directions to vary pump displacement, the combination of a cam for moving said member in one direction and for limiting its movement in the opposite direction, a

cam track arranged upon said cam and includring a neutral track section extending parallel to the path of said cam and a displacement varying section inclined to said path, means for urging said member in said opposite direction and for holding said contact against said cam track, andmeans for movingsaid cam in opposite directions selectively to move said cam track across said contact to effect movement of said member and thereby cause a variation in pump displacement,

said cam being so formed that said cam track, drops abruptly from one to the other of said -motor means for moving said cam in opposite directions selectively to effect movement of said member in opposite directions selectively, means for supplying motive fluid to said servo-motor, l means including a pilot valve shiftable from and;

to a neutral position to effect movement of said cam from and to its neutral position, a control operable by an external force from and to a neutral position for moving said valve from and to its neutral position, and spring means for returning'said control to it neutral positicn upcn removal of'said external forces 20. In a pump having a displacement varying,

member shiftable in opposite directions to vary pump displacement, the combination of a cam for moving said member in one direction and for limiting its movement in the opposite direction, a contact on said member,means for urging said 'member in said opposite direction'and for holding said contact against the, face of said cam, servo-motor means for moving said cam in opposite directions selectively to eiTect movement of said 'member in opposite directions selectively, means for supplying motive fluid to said servomotor means including a .pilot valveconstantly urged in one direction and hiftable from and to a neutral position to effect movement of said cam from and to its neutral position, a follow-up mechanism for transmitting motion from said cam to said pilot valve, a control associated with said follow-up mechanism and being operable by an external force from and to a neutral position to efiect movement of said valve from and to its neutral position, and spring means for returning said control to its neutral position upon removal of said external force.

21. In a hydrodynamic machine having a member shiftable in opposite directions to vary the displacement of said machine, the combination of an element movable in opposite directions from a neutral position for efiecting movement of said member in opposite directions, a control operable by an external force from and to a neutral position for efiecting movement of said element, and spring means for returning said control to its neutral position upon removal of said external force.

22. In a hydrohynamic machine having an inlet and an outlet, the combination of a cylindrical reaction member; an annular'cylinder barrel arranged within aid member and having a plurality of radial cylinders arranged therein with the outer ends thereof arranged in a row extending around the periphery of said cylinder barrel, alternate cylinders in said row being inclined in opposite directions so that the inner ends thereof are arranged close together and form a double staggered row in the inner periphery'of said cylinder barrel with sufiicient wall thickness between adjacent cylinders, means for rotating said cylinder barrel, a piston fitted in each cylinder and engaging said member to be reciprocated thereby during rotation of said cylinder barrel, and means for connecting each cylinder with said inlet and said outlet alternately as said cylinder barrel rotates.

WALTER FERRIS; ADOLF R. GRAD. 

